THE RESISTANCE OF RICE VARIETIES TO THE BROWN PLANTHOPPER, NILAPARVATA LVGENS (STAL)

The resistance of 9 rice varieties to the brown planthopper (BPH), Nilaparvata lu-gens (Stal), was tested by using the seedling bulk screening method. Among the 9 varieties tested, Mudgo and 7105 was highly resistant (HR); while Triveni, Fubaoai 21, Fubaoai 1, Baosyan 2, Zhungshanhong and Gubao 117 were moderately resistant (MR). It was found that an age-related increase in resistance of the plant to the BPH was evident in the moderately resistant varieties, but this was not found in the high resistant ones.The nature of the resistance of MR varieties, including Fubaoai 21, Baosyan 2, Zhungshanhong and Triveni, and HR variety 7105 was studied. The results were as follows:1)The BPH did not prefer the HR varieties on which the insects had low food uptake, slow development, high mortality, and low fecundity and egg hatchability, due to the presence of antibiotic factors. Therefore the population growth on HR varieties was suppressed.2)The MR varieties of Fubaoai 21 and Triveni were preferred by BPH for feeding at 10-day old plants, but they were not preferred at 45-day old plants, on which the caged insects had retarded development and low levels of survival and fecundity. Thus on the above mentioned two varieties the insect populations were smaller as compared with that on the susceptible TN 1. Except at 60-day old plants, no significantly adverse effects of the varieties such as Baosyan 2 and Zhungshanhong at 45-day old plants on this insect were observed.Thus, the moderate resistance in the varieties Fubaoai 21 and Triveni is caused by the strong antibiosis and some level of tolerance, but the resistance in Baosyan 2 and Zhungshanhong is due to week antibiosis and high tolerance. In general, the tolerance increased with the increase of the age of the rice plant.